I was sat here thinking about different tactics and army lists one night and started thinking about counter Tyranid tactics.I kept coming back to the Marines problem of not enough firepower/men on the table then i came up with the idea of the Marine horde-sacrifice tanks/elites/overpowered units to just get men on the field.
I ran this through my interactive army list and found that for 2000 points you could get 121 Marines on the field-now thats allot of fire power.
OK you don't have massive Devastator Squads (but i always found them to be an under used resource) or Elites but this is just a wall of bolter death
I have posted the Army list
HERE so you can see how it breaks down and where the Marines and what special weapons I have taken are.
Deployment wise I would set the Tactical squads as a wall to do the main bulk of the firing with the Heavy Support choices acting as a tactical reserve to plug gaps in the lines/add weight of fire at closer ranges and let the Fast Attack choices hang back to provide counter charge capability.
The commander is purely on the table to keep the army legal and give the higher leadership-not as the usual close combat monster that they become.
Don't forget the idea here is to shoot the proverbial out of the enemy before they reach you and mop up the close combat with your superior numbers.